G.f. A(x) satisfies A(x) = 1 / ((1 - x) * (1 - 2 * x * A(x^4))).

Terms

a(0) =1a(1) =3a(2) =7a(3) =15a(4) =31a(5) =69a(6) =157a(7) =357a(8) =805a(9) =1811a(10) =4079a(11) =9199a(12) =20751a(13) =46797a(14) =105517a(15) =237917a(16) =536477a(17) =1209723a(18) =2727839a(19) =6151031a(20) =13869991a(21) =31275569a(22) =70523657a(23) =159024657a(24) =358586513a(25) =808580683a(26) =1823277559a(27) =4111329079a(28) =9270682359a(29) =20904566081